Hi,   I'm new to SAS and started to program and tests some things. Now I found a strange behavior and maybe someone is nice and explains it to me. This is my code: DATA one;  INPUT id v3 v4;  DATALINES;  1 10 100  2 15 150  3 20 200  ; DATA two;  INPUT id v3 v4;  DATALINES;  4 1000 10000  5 1500 15000  5 2000 20000  7  800 30000  ; DATA theData;     SET one;     OUTPUT;     IF _N_ THEN DO;     IF id = 2 THEN DO;     SET two (WHERE=(id = 5));     OUTPUT;     END;     END; RUN; PROC PRINT DATA=one; TITLE "one"; RUN; PROC PRINT DATA=two; TITLE "two"; RUN; PROC PRINT DATA=theData; TITLE "theData"; RUN;     The result is: # id v3 v41234 1 10 100 2 15 150 5 1500 15000 3 20 200   I expected one more row,  "5 2000 20000" between  5 1500 15000 and  3 20 200   Am I'm wrong? Best, Markus ... View more